Such a tool comprises what could be referred to as a propelling engine, arranged for driving in motion, under the firing action of a fuel (gas or powder, more particularly), a piston (or a weight) provided with a rod for driving a fastening member into a supporting material.
In the front part of the tool, there is a fastener guide wherein the fastener to be driven is arranged. Firing could only occur after the tool is being abutted, through the fastener guide, against the supporting material.
The penetration depth of the fastening member into the supporting material depends on the length thereof and on the length of the piston rod projecting outside the fastener guide at the end of the shot. It is thus understood that it was desired to adjust such a depth of drive as a function, precisely, of the length of the fastener, of the need to embed the head thereof into the supporting material, of the wish not to burst out the accessory, if it is to be fixed with the supporting material, or even and for instance, of the concern not to burst out the supporting material or not to form a scratched area.
There have already been suggested to provide depth of drive adjustment devices, but which are very complex. After a first part has been lifted, two screws are to be unscrewed, a key is to be moved, the screws are to be screwed again, and the part should be put back in position, all this occurring using tools.
The invention thus aims to provide a tool with a particularly simple adjustment device.
Thus, this invention relates to a hand fastening tool, comprising an engine for propelling a piston, comprising a shaft for driving a fastening member into a supporting material and through a pin guide, with means for adjusting the depth of drive of the piston shaft outside the pin guide at the end of the propulsion and stop of the piston in abutment against stop means, characterised in that the pin guide is mounted free in translation and the depth of drive adjusting means comprise a adjustment knurl with a knurl shaft arranged to be in abutment against the pin guide and to push the pin guide forwards under the action of the knurl rotation.
The position of the piston in the tool at the end of the propulsion, after a shot, being predetermined by the stopping means, the more the pin guide is pushed forwards, the more the depth of drive of the piston shaft is reduced.
It is to be noticed that if the operator, after a shot, notices that he had turned the knurl too much, before the following shot, he will turn the knurl in the opposite direction and, upon the new abutment of the tool, the pin guide will return back to be located in abutment against the knurl shaft in a better position.
It should be noticed that the tool of the application EP 1,934,018 also comprises a means for adjusting the depth of drive, with an adjustment knurl as well. But such a knurl directly cooperates with a sensor rod, as well in one direction as in the other one, the portion of the sensor rod cooperating with the knurl being threaded so as to get very accurate adjustments. The U.S. Pat. No. 5,385,286 discloses depth adjusting means of approximately the same type.